Amanda Thatcher's composure and dignity at the funeral of her beloved grandmother Margaret Thatcher bore more than a passing resemblance to the Iron Lady herself.

The only daughter of the late Prime Minister's son Sir Mark and his American former wife Diane read from St Paul's Letter to the Ephesians VI. 10-18.

Dressed elegantly in black, her voice crystal clear but faltering occasionally, Amanda, 19, spoke before a congregation of 2,300 dignitaries including the Queen and the Duke of Edinburgh, and statesmen from around the world.

The passage which is traditionally read at funeral services for all holders of the Order of the Garter included the words:

"Be strong in the Lord, and in the power of his might.

"Put on the whole armour of God, that ye may be able to stand against the wiles of the devil. For we wrestle not against flesh and blood, but against principalities, against powers, against the rulers of the darkness of this world, against spiritual wickedness in high places."

Many in St Paul's Cathedral were openly emotional as she stood at the lectern. The only other reading came from Prime Minister David Cameron.

Like her 24-year-old brother Michael, Amanda is a committed Christian. She is currently studying at the University of Richmond in Virginia.

The parallels with the iconic politician don't end with her confidence at Wednesday's service – on graduating from school the teenager was voted "the person most likely to change the world" by her peers.

She and Michael, a chemistry graduate like their grandmother, flew in at the weekend from Dallas, Texas. They were brought up in the US city by their mother, who has since remarried.

At the start of proceedings, Baroness Thatcher's grandchildren walked ahead of her coffin down the aisle bearing the Prime Minister's Order of the Garter and the Order of Merit on a cushion.

Amanda was given a central role at the request of her grandmother following her disappointment as a nine-year-old at not being able to read at the final farewell for her grandfather Denis.

She listened as the Bishop of London, Richard Chartres, said in his sermon that "it must be difficult for members of her family... to recognise the wife, mother and grandmother in the mythological figure". He added "our hearts go out to (them)".

Once the service was over, the Thatcher family stood on the steps of the cathedral to see the coffin borne on its final journey, the applause of the Baroness' supporters ringing in their ears.

The group was completed by Mark's second wife Sarah, his twin sister Carol and her partner Marco Grass.

All the women dipped low curtseys when Mark introduced them to the Queen.

Arriving from her home in Switzerland a few days ago, Carol said it would be a "tough and tearful week" and she felt like anyone else who had just lost a second parent.

Her family can at least be comforted that the grocer's daughter who became one of the most powerful figures in the world was given an impressive and dignified farewell.